POR15, undercoat, or sprayon bedliner?
POR-15, but I think I'm going to try the Eastwood Encapsulator paint because several people now have told me they like it better than the POR-15. I hope the lid is easier to open than the POR-15 one!
You can paint over POR-15, just read the data sheet, follow the directions and it's not an issue.
http://www.por15.com/Data Sheets/POR15ApplicationInfo.pdf
Read the tip sheets too. Basically, just read about how to do it like with anything else. (all at the below link)
http://www.por15.com/quickindex.asp